In this age of the growing importance of information, there is a great urgent demand for organic dye compounds which absorb near infrared radiation. Their application is now extending beyond conventional field, for example, photo-detecting semiconductor device and filter material for use in plasma display; which solely utilize the near infrared radiation-shielding property of such an organic dye compound, towards the field of information storage such as optical recording medium using laser as light source, optical card, printing plate, thermocopy and thermal recording which utilize an energy converted from near infrared radiation by such an organic dye compound.
The properties required for organic dye compounds to be subjected to such a use are to be appropriate with respect to optical absorption characteristic and large with respect to optical resistance against ambient light such as natural or artificial light in the near infrared region and also with respect to solubility in solvents. Typical organic dye compounds as proposed heretofore are, for example, anthraquinone, phthalocyanine and cyanine dyes (see, for example, Japanese Patent Kokai Nos. 116611/99, 202592/02 and 167343/03): Among these, anthraquinone dye has been deemed to be advantageous with respect to optical resistance but disadvantageous with respect to optical absorption characteristic, while phthalocyanine dye, advantageous with respect to both optical absorption characteristic and optical resistance but disadvantageous with respect to solubility in solvents. Although cyanine dye is advantageous in both optical absorption characteristic and solubility, conventional cyanine dye has the demerit that it is poorer with respect to optical resistance.
In view of such situation, the objective of this invention is to provide an organic dye compound which is superior in optical absorption characteristic and optical resistance in the near infrared region and also in solubility so as to extend the range of choosing organic dye compounds as light absorbing organic material in the fields as described above.